The present invention relates generally to electronically scanned antennas and, more particularly, to an electronic scanned antenna with a microelectromechanical system (MEMS) radio frequency (RF) phase shifter.
Advanced airborne and space based radar systems heretofore have used electronically scanned antennas (ESA) including thousands of radiating elements. For example, large fire control radars which engage multiple targets simultaneously may use ESAs to provide the required power aperture product.
Space based lens architecture is one approach to realizing ESA for airborne and space based radar systems. However, when the space based lens architecture is utilized at higher frequencies, for example, the X-band, and more active components such as phase shifters are packaged within a given area, weight, increased thermal density, and power consumption may deleteriously affect the cost and applicability of such systems.
Heretofore, phase shifter circuits for electronically scanned lens array antennas have included ferrites, PIN diodes and FET switch devices. These phase shifters are heavy, consume a considerable amount of DC power, and are expensive. Also, the implementation of PIN diodes and FET switches into RF phase shifter circuitry is complicated by the need of an additional DC biasing circuit along the RF path. The DC biasing circuit needed by PIN diodes and FET switches limits the phase shifter frequency performance and increases RF losses. Populating the ESA with presently available transmit/receive (T/R) modules is undesirable due to high costs, poor heat dissipation and inefficient power consumption. In sum, the weight, cost and performance of available phase shifter circuits fall short of what is needed for space based radar and communication ESA""s, where thousands of these devices are used.
The present invention provides a microelectromechanical system (MEMS) steerable electronically scanned lens array (ESA) antenna. According to an aspect of the invention, the MEMS ESA antenna is steerable in the E-plane using MEMS phase shifter modules, and steerable in the H-plane using MEMS phase shifter modules. The MEMS ESA antenna includes a MEMS E-plane steerable lens array and a MEMS H-plane steerable linear array. The MEMS E-plane steerable lens array includes first and second arrays of wide band radiating elements, and an array of MEMS E-plane phase shifter modules disposed between the first and second arrays of radiating elements. The MEMS H-plane steerable linear array includes a continuous transverse stub (CTS) feed array and an array of MEMS H-plane phase shifter modules at an input of the CTS feed array. The MEMS H-plane steerable linear array is disposed adjacent the first array of radiating elements of the MEMS E-plane steerable lens array for providing a planar wave front in the near field. The H-plane phase shifter modules shift RF signals input into the CTS feed array based on the phase settings of the H-plane phase shifter modules, and the E-plane phase shifter modules steer a beam radiated from the CTS feed array in an E-plane based on the phase settings of the E-plane phase shifter modules.
According to another aspect of the invention, there is provided a method of frequency scanning radio frequency energy, comprising the steps of inputting radio frequency (RF) energy into an array of MEMS H-plane phase shifter modules; adjusting the phase of the RF energy based on the phase settings of the MEMS H-plane phase phase shifter modules; radiating the H-plane phase adjusted RF signals through a plurality of CTS radiating elements in the form of a plane wave in the near field; emitting the H-plane phase adjusted RF plane wave into an input aperture of a MEMS E-plane steerable lens array including an array of MEMS E-plane phase shifter modules; converting the RF plane wave into discrete RF signals; adjusting the phase of the discrete RF signals based on the phase settings of the MEMS E-plane phase shifter modules; and radiating the H-plane and E-plane adjusted RF signals through a radiating aperture of the MEMS E-plane steerable lens array, thereby recombining the RF signals and forming an antenna beam.